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Cambridge, Mass., Museum of Comparative Zoology, Harvard University. 

no.1 21 -1 78 (1 960-1 962): 7 
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Museum of Comparative Zoology 

Cambridge, ^Mass. 

Decembkr 20, 



By Curt 


maximum size of fossil animal groups, whether mammals. 

reptiles, or invertebrates lias always l)eeii a fasciiiatiiig subject 
of inquiry, because phyletie size increase is one of the important 
trends that dominate the c^volution of living things. In the case 
of large animals, tlie evidence is often hard to assenil)le because 
their remains are difficadt to obtain, to transport, and to store. 
Squids are the largest living invertebrates and a ti*aditinn has 
been lianded down in paleontolos'ical literature that the largest 
fossil invertebrates likewise are to be found among the cephalo- 
pods, but few accurate data are to be found in published sources 
which are nOAV readily availal)le. 

Among the nautiloid cephalupods, it has long been suspected 
the Endoceratida furnished the real giants, but no accurate 
measurements in support of this statement are available. 

Clarke (1S97) stated that entire shells of Came voce ras pro- 
tciformc, 10 to 15 feet long (3 to 5 meters), had been found in 
the Lliddle Ordovician of IMinnesota. In the same publication, 
Clarke figured an internal cast of part of a siphnnele, from the 
base of the l)ody chamber to the adapical end of the spiess, 
which v/as 3 feet and 3 inclies long. Miller and Kununel (1944) 
described and illustrated additional species of these :\Iiddle 
Ordovician eucloeeroids from ]\riiinc.sota, which are deposited in 
the Carnegie Mnsenm. One of tlieir paratypes of Endoccras 
clarkei measured 750 mm loim-, is septate throughout and is 
not complete, adapically or adorally. The holotype of End<^rrras 
graciUimnm Miller and Kununel (1944) measured 670 mm in 

1 Publication authonzea by the ]>irect(H'. V. S. G«M)l(»gical Survey 
-U. S. Geological Survey, Denver, Colo. 
3 Museum of Comparative Zoology. 


BREVrORA No. 128 

leiig'tli, again an inrompli^te sptHMiiKai consisting' only of plirag- 
moeone. These same antliors deseribed a new species, Endoccras 
di covifhi nse, on two i)oi*ti()ns of llu? iiiteviial mold of tlie plirag- 
moeone from the Dc^corah formation, AVinneskiok County, Iowa. 
The larger portion is about G25 nini lonii' and the length of the 

smaller measures about 320 nun. Thev estimated the interval 
between the two pieces as about 115 mm, so the total length of 

this jjliragmocone was about 1,0G0 nnn. These authors also men- 
tioned that there is on display in the Chicago Natural History 
Museum a larger endoceroid that measures 6 feet in length. 

(1027) noted the occurrence, in Middle OrdoAucian 
limestones of Estonia, of endoceroids as nuicli as 5 meters long, 
but gave no further details. Flower (lOoT)) stated that specimens 
12 feet in length had been collected and added that he was ^^not 
Avholly inclined to discredit a report of an (Midoceroid found 
in a quarry near AVatertoAvn, New York, Avhicli was measured 
before it was broken up and found to attain a length of 30 feet.^' 
As far as we have been able to ascertain, these somewhat vague 
statements are all that is presently available in the published rec- 
ord on the subject of the maximum size of endoceroid cep- 

It does not seem to be generally known that the ^Museum of 
Comparative Zoology at Harvard University possesses what ap- 
pears to be the largest fragment of an endoceroid cephalopod 
on display anywh(MT in the world. As Flowtn- (l!)o5) has stated, 
''the removal of even reasonably complete si)(*cimens involves 
something very close to rpiarrying operations, storing them is 
anotlier problem." The specimen in the collections of the 
scum of Comparative Zoology is, therefore, probably uinrpie 
in museums of the world. 

The specimen measures 3,000 nmi in haigth but is not com- 
plete, adorally or adapically. In general the preservation is fair, 
but as a result of weathering and crushing the full diameter 
of the conch is preserved oidy in one plane, and in the other 
plane the onter shell is removed exposing traces of septa and 
in places the siphuncle. The first recognizable septa are 500 mm 
fi'om the adoral end but the whole specimen could well be 
phragmocone as this adoral 500 mm is slightly crushed and 


weathered and one cannot tell Avhether septa are present oi 

)sent. The adoral diameter of the specimen is 280 mm. The 
eonch tapers at a uniform rate and the adapical diameter meas- 
ures 120 mm. 



Figure 1 — Large endoceroid on exliibit in the Mnseiim of 




No. 12S 

The 8i'i)ta slojx^ adapically at au anglo of about 45^^ and in 
the niid-pai*t of tho speeinion are spaced 17 to 20 mm apart. TJic 
sii)liunclc is visible oidy on the adapieal lialf of the specimen. 
About 1,000 mm fi-om tlie adoral end of the shell the siphuncle 

has a diameter of about 93 mm; at 1,750 nun from tlie adoral 
end of the sIk^II tlie sipliuuele has a <liameter of 75 mm. The 
first endocones appear 2,000 mm behind the adoral end of the 
slu_dl. Tlie spi(^ss UK^asurrs 510 mm in length. The surface of the 
shell bears faint annulations that are spaced approximately 10 
to 12 mm ai)art. 


f « . 

• •••■■• 


Adoral diaiiioter .... 

Diiuiieter ],000 luiu fruni adoral ciul.. 

Diameter 3,750 lum from adoral end .. 

Adapieal diameter . . . 

Diameter of sipluinele 1,000 mm from adoral end 

Diameter of six'^luincle 1,750 mm from adoral end . . 

Spiess lengtli . 

a • 

* * - -P * 

#■ B « « fl 

ff «■ ■ 

" « ■ 

3,000 mm 
. , 280 mm 

« * * '* 

» * * » * 

t » m 

« * 

. . 220 mm 

. , .170 mm 
.120 mm 
... 95 mm 

. . 75 mm 
.510 mm 

A graphical reeonstriietion of the shell on the basis of these 
measurements sliows that the entire fossil from its presently pre- 
served adoral end to the apex may have measured about 


Tlie total h^ngth of tlie body eliamber is a matter of guesswork. 
There are few pul)lished and illustrated records of 'dny straight 
fossil cephalopod sliells, eumplete from apex to aperture, which 
are more than a foot or so long. In short shells the ratio of bod}^ 
chamber to phragmocone may he high, even larger than 1:1. 


AVitli increasing total length of conch, however, ratio of body 
I'liamber to j^hragnuH'one is likely to decrease, although no defi- 
nite figures can ho stated. In a specimen of A('tf)iOceras hcloifensc 
(Foerste and Teichert, 1930, pL 28), which was 450 mm long, the 
ratio of body chamber to pliragmocone was about 1 :2. Leith 
(1912) described a specimen of Lamhcoccrus lam'bii (AVhiteaves) 
which Avas 45.5 in. (1,155 nun) long. He estimated the total 
length of the shell at 1,105 nun. The l)ody chamber was almost 
wholly pr(*served and not more than 250 mm long. Ratio of 
body chamber to ]>liragmocone was thus 1 :4.6 in this specimen. 
It sliould be noted, however, that both Actinoccras hdoitcnsc 
and Lamhcoccra^ lamlrii have body chambers with constricted 


a|)(M*tureSj wliereas no eiidoeHn'oids with constricted apertures 
are known. It seems ph^'siologically plausible that in hirge 
straight ceplialopod shells the aniiiial should have a better 

)er with constricted apertnre than on 
one Avitli an nneonstrieted aperture; therefore, in shells which 
expanded uniformly from the apex to the aperture, like the 
enduceroids, the animal itself, and thus its body chamber, should 
have been relativclv larger. 

In a juvenile specimen of a straight ammonoid, Baculitcs 

ovatuSy Trueman (1911) determined the ratio of length of body 
chamber to phragmocone as 1 :0.7, but in adult shells this ratio 
becomes much smaller. If we assume the ratio of length of bodv 
chamber to phragmocone in endoceroids to be inore like that 
of Actinoceras heJoitoise we arrive at a length of the body 
chamber for the Harvard Endoccras of 2,650 mm and for the en- 
tire shell of 8,150 mm, or 28 feet. This is a conservative esti- 
mate, yet close to the possible maximum figure of 30 feet men- 
tioned bv Flower. 

Add to this the leng-tli of the tonacles ^Yliicli must have ex- 
tended a considerable distance in front of the aperture, cer- 
tainly no less than half the length of the l)ody chamber, and 

\ve have an invertel)rate animal considerably longer than 30 
feet — a truly imposing size. Today's giant squid, ArcJiiteutlns, 
rivals and slishtlv exceeds in length the largest extinct endocer- 

oids. Spiirck (1028) records specimens of Arcliiiciithis dux 
fi-om the North Atlantic, Avashed ashore on the Norwegian Coast, 
that have body lengths of up to 2 meters and tentaeles as much 
as 10 meters long. The largest specimen to our knowledge is 
that of Archifeuthis Jutiueyi? recorded by Ycrrill (1870, ]>. 196) 

whicli measures 624 inches (17 meters). There is a model in 
the ]\Iusoum of Comparative Zoology of a specimen of Archi- 
Icitthts princcps, which was washed ashoi'c in Newfoundland, 
which measures about lo meters in length. More recently, Lane 
(1960, pp. 198-227) has critically reviewed a larger number of 
reports of finds of and <MU'(.)unters with giant squids. He is in- 
clined to believe that individuals of Arclnicnihh or some other 
o-enus, as vet undescribed, mav reach overall lengths of some 

70 feet. 

While the Harvard specimen represents l)y far the largest 

nautiloid cephalopod on Avhich accurate data are now available, 

it is interesting to compare it with the largest anniionoid on 

record. This is Paclnjdiscus seppenradense Landois from the 

6 BREVTORA No, 128 

)per Cretaceous of western Gonnany (LandoiSj 189.1^ 1808). 
Ill 1895, Landois first described this fossil ammonoid whose shell 
was 1,800 iniii in diaim^ter and in which the last camera was 
550 mm high. Landois^ reeonstrnetion provided the animal Avitli 
a body clianiber eqnivalent to only une-fourtli of a eouiidcte 
wliorl. From this lie conelnded that the total diameter of tho 
complete specimen uf his ammonoid had been about 2,550 mm. 
From later studies (Trncman, 1941) it is, however, likely that 
Landois' estimate of the length and bulk of living chamber Avas 
too low. If the body chaml)er of PacJnjrJIscus scppcDradense was 
eqnivalent, as is more likely, to three-fourths or one full volu- 
tion of the shell, the diameter of the adult shell of this ammonite 
would have lieen of the order of 3,500 mm, or more than 10 feet. 
A very approximate graphic plot of a shell of this kind shows 
that the total length of the shell of Pachyfliscus ^eppciirnrlrn^Cy 

when unrolled, would have been of the order ot 60 feet, or 
roughly twice as long as that of tiie largest endoceroid. 

r paper Landois (1898) attempted to estimate the 
weight of these giant cepludopods. On the basis of his estimated 
measurements he arriv(?d at a total weight of the ammonite 
as 1,455 ke:, or 750 k^ for the weight of the aniuuil itself, and 
705 kg for the weight of the shell. 

AVe shall abstain from any attempt to iiielieate exact weights 
of the large emloceroids. The order of magnitude was almost 
certainlv the same as that inferred bv Landois for the giant 
V achy disc US y something of the order of 1 ton (about 1000 kg). 
It must be assumed tliat the weight of sliell and 


Avhich for a h^nuth of i)\vY 5,000 mm was entirelv filled with 
calcareous di^posits, balanced tlu* buo^^ancy provided by the 
empty camerae and confined the animal to a strictly benthonic 
existence. Fmv, if any, fossil invertebrates ever surpassed them 

in bulk weight and size. 

One other point deserves attention : Phyletic size increase 
is a trend that as a rule continues until the end, or very close 
to the end of the evolutionary life of a particular group of 
organisms, as, for example, in the ammonoids. The endoceratids, 
however, reached their maximum size long before the time of 
extinction, in fact I'clativelv earlv in their evolution. In North 
America, as well as in northern Europe, endoceroid cephalopods 
survive to tlie end of the Ordovieian period, but reach their 
maximal size during ]\Iiddle Ordovieian time (Teichert, 1030, 
pp. 235-236). 



Clarke, J. M. 

1S97. Tlie Lower Silurinii Ceplinlupodn of ^liiniesota. Geolot^y of 

Minnesota, vol. 3, pt, 2, Paleontology, pp. 761-812, pis. 47-60. 

Flower, li. II. 

1955. Status of enJuceroid classification. Jour. Palcontoloj^y, vol 

29, no. 3, pp. 329-371, 

FoKRSTE, A. F., and Teiciiert, Curt 

1930. Tlic actinoceroids of east-central Xortli America. Denison Univ 

Bull., Sci. Lab. Jour., vol. 25, pp. 201-296, pis. 27-59. 

Landois, IL 

1895. Die Riesenanimoniten von Seppenrade, Pachi/discu.^, Zittel, Sep- 

penradense II. Laiulois. Westfiil. Provinzial, Ver, Wiss. imd 

/r\ -^ 

Kunst. f. 1894/95, vol. 23, pp. 99-108, 2 pis. 
1898. Gewichtsverhaltnisse der Eiesen-Amnioniten. Ihul., vol. 26, i>p. 


Lane, F. W. 

1957. Kingdom of the Octopus. Jarrulds, London. 2SG pp. 

Leitit, E. I. 

1942. Xotes on tlie ceplialopod Lamhcoccras lamhil from Manitoba. 

Jour. Paleontology, vol. IG, no. 1, pp. 130-132, 1 text-fig,, pi. 22. 

.Miller, A. K., and Kummel, Berxtiard 

1944. Some large straight Ordovician cephalopods from Minnesota 

Annals Carnegie Museum, vol. 30, pp. 19-38, 4 pis. 

Sparck, E AG mar 

1928. Xordens Dyreverden. Ilenrik Kopi;)el, Copenhagen, 658 i^p. 

Teichert, Curt 

1927. Der estlandische Glint. Xatur u. Museum, vol. 57, pp. 264 

272, 7 figs. 
1930. Biostratigraphie der Poramboniten. Xeues Jahrb. f. Mineral 

etc., Beil. Ed., Abt. B, pp. 177-246, 8 figs., 4 pis. 

Truemax, A. E. 

1941. The ammonite body-chamber, with special reference to the 

liuovancv and mode of life of the living ammonite. Quart. Jour, 
Geol. Soe. London, vol. 9(^, pip. 339-378. 

Vi:rrill, a. E. 

1879. The cephalopods of the northeastern coast of America. Trans. 

Conn. Acad. Sci., vol. 5, pp. 177-476, pis. 25-56.